Eliminate make_cleanup_obstack_free, introduce auto_obstack

This commit eliminates make_cleanup_obstack_free, replacing it with a
new auto_obstack type that inherits obstack to add cdtors.

These changes in the parsers may not be obvious:

 -  obstack_init (&name_obstack);
 -  make_cleanup_obstack_free (&name_obstack);
 +  name_obstack.clear ();

Here, the 'name_obstack' variable is a global.  The change means that
the obstack's contents from a previous parse will stay around until
the next parsing starts.  I.e., memory won't be reclaimed until then.
I don't think that's a problem, these objects don't really grow much
at all.

The other option I tried was to add a separate type that is like
auto_obstack but manages an external obstack, just for those cases.  I
like the current approach better as that other approach adds more
boilerplate and yet another type to learn.

gdb/ChangeLog:
2017-06-27  Pedro Alves  <palves@redhat.com>

	* c-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(c_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* c-lang.c (evaluate_subexp_c): Use auto_obstack.
	* d-exp.y (name_obstack): Now an auto_obstack.
	(yylex): Use auto_obstack::clear.
	(d_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* dwarf2loc.c (fetch_const_value_from_synthetic_pointer): Use
	auto_obstack.
	* dwarf2read.c (create_addrmap_from_index)
	(dwarf2_build_psymtabs_hard)
	(update_enumeration_type_from_children): Likewise.
	* gdb_obstack.h (auto_obstack): New type.
	* go-exp.y (name_obstack): Now an auto_obstack.
	(build_packaged_name): Use auto_obstack::clear.
	(go_parse): Use auto_obstack::clear instead of reinitializing and
	freeing the obstack.
	* linux-tdep.c (linux_make_mappings_corefile_notes): Use
	auto_obstack.
	* printcmd.c (printf_wide_c_string, ui_printf): Use auto_obstack.
	* rust-exp.y (work_obstack): Now an auto_obstack.
	(rust_parse, rust_lex_tests): Use auto_obstack::clear instead of
	reinitializing and freeing the obstack.
	* utils.c (do_obstack_free, make_cleanup_obstack_free): Delete.
	(host_char_to_target): Use auto_obstack.
	* utils.h (make_cleanup_obstack_free): Delete declaration.
	* valprint.c (generic_emit_char, generic_printstr): Use
	auto_obstack.

1 files changed, 4 insertions, 14 deletions

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 2369d4b..2f70bd2 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -3060,13 +3060,11 @@ create_addrmap_from_index (struct objfile *objfile, struct mapped_index *index)
 {
   struct gdbarch *gdbarch = get_objfile_arch (objfile);
   const gdb_byte *iter, *end;
-  struct obstack temp_obstack;
   struct addrmap *mutable_map;
-  struct cleanup *cleanup;
   CORE_ADDR baseaddr;
 
-  obstack_init (&temp_obstack);
-  cleanup = make_cleanup_obstack_free (&temp_obstack);
+  auto_obstack temp_obstack;
+
   mutable_map = addrmap_create_mutable (&temp_obstack);
 
   iter = index->address_table;
@@ -3107,7 +3105,6 @@ create_addrmap_from_index (struct objfile *objfile, struct mapped_index *index)
 
   objfile->psymtabs_addrmap = addrmap_create_fixed (mutable_map,
 						    &objfile->objfile_obstack);
-  do_cleanups (cleanup);
 }
 
 /* The hash function for strings in the mapped index.  This is the same as
@@ -6626,7 +6623,6 @@ static void
 dwarf2_build_psymtabs_hard (struct objfile *objfile)
 {
   struct cleanup *back_to, *addrmap_cleanup;
-  struct obstack temp_obstack;
   int i;
 
   if (dwarf_read_debug)
@@ -6649,8 +6645,7 @@ dwarf2_build_psymtabs_hard (struct objfile *objfile)
 
   /* Create a temporary address map on a temporary obstack.  We later
      copy this to the final obstack.  */
-  obstack_init (&temp_obstack);
-  make_cleanup_obstack_free (&temp_obstack);
+  auto_obstack temp_obstack;
   objfile->psymtabs_addrmap = addrmap_create_mutable (&temp_obstack);
   addrmap_cleanup = make_cleanup (psymtabs_addrmap_cleanup, objfile);
 
@@ -13796,15 +13791,12 @@ update_enumeration_type_from_children (struct die_info *die,
 				       struct type *type,
 				       struct dwarf2_cu *cu)
 {
-  struct obstack obstack;
   struct die_info *child_die;
   int unsigned_enum = 1;
   int flag_enum = 1;
   ULONGEST mask = 0;
-  struct cleanup *old_chain;
 
-  obstack_init (&obstack);
-  old_chain = make_cleanup_obstack_free (&obstack);
+  auto_obstack obstack;
 
   for (child_die = die->child;
        child_die != NULL && child_die->tag;
@@ -13849,8 +13841,6 @@ update_enumeration_type_from_children (struct die_info *die,
     TYPE_UNSIGNED (type) = 1;
   if (flag_enum)
     TYPE_FLAG_ENUM (type) = 1;
-
-  do_cleanups (old_chain);
 }
 
 /* Given a DW_AT_enumeration_type die, set its type.  We do not